preserve offsets when sending client to screen

for that purpose, move sendToScreen and updateLayer
functions from Workspace to Client, keep wrappers

BUG: 327361
FIXED-IN: 4.11.6
REVIEW: 114078

client.h

@@ -346,6 +346,8 @@ public:
     void setDesktop(int);
     void setOnAllDesktops(bool set);
 
+    void sendToScreen(int screen);
+
     virtual QStringList activities() const;
     void setOnActivity(const QString &activity, bool enable);
     void setOnAllActivities(bool set);
@@ -405,6 +407,7 @@ public:
     virtual Layer layer() const;
     Layer belongsToLayer() const;
     void invalidateLayer();
+    void updateLayer();
     int sessionStackingOrder() const;
 
     void setModal(bool modal);

geometry.cpp

@@ -3266,4 +3266,67 @@ void Client::setQuickTileMode(QuickTileMode mode, bool keyboard)
     }
 }
 
+void Client::sendToScreen(int newScreen)
+{
+    newScreen = rules()->checkScreen(newScreen);
+    if (isActive()) {
+        screens()->setCurrent(newScreen);
+        // might impact the layer of a fullscreen window
+        foreach (Client *cc, workspace()->clientList()) {
+            if (cc->isFullScreen() && cc->screen() == newScreen) {
+                cc->updateLayer();
+            }
+        }
+    }
+    if (screen() == newScreen)   // Don't use isOnScreen(), that's true even when only partially
+        return;
+
+    GeometryUpdatesBlocker blocker(this);
+
+    // operating on the maximized / quicktiled window would leave the old geom_restore behind,
+    // so we clear the state first
+    MaximizeMode maxMode = maximizeMode();
+    QuickTileMode qtMode = (QuickTileMode)quick_tile_mode;
+    maximize(MaximizeRestore);
+    setQuickTileMode(QuickTileNone);
+
+    QRect oldScreenArea = workspace()->clientArea(MaximizeArea, this);
+    QRect screenArea = workspace()->clientArea(MaximizeArea, newScreen, desktop());
+    QRect oldGeom = geometry();
+    QRect newGeom = oldGeom;
+    // move the window to have the same relative position to the center of the screen
+    // (i.e. one near the middle of the right edge will also end up near the middle of the right edge)
+    QPoint center = newGeom.center() - oldScreenArea.center();
+    center.setX(center.x() * screenArea.width() / oldScreenArea.width());
+    center.setY(center.y() * screenArea.height() / oldScreenArea.height());
+    center += screenArea.center();
+    newGeom.moveCenter(center);
+    setGeometry(newGeom);
+    // align geom_restore - checkWorkspacePosition operates on it
+    geom_restore = newGeom;
+
+    // If the window was inside the old screen area, explicitly make sure its inside also the new screen area.
+    // Calling checkWorkspacePosition() should ensure that, but when moving to a small screen the window could
+    // be big enough to overlap outside of the new screen area, making struts from other screens come into effect,
+    // which could alter the resulting geometry.
+    if (oldScreenArea.contains(oldGeom))
+        keepInArea(screenArea);
+    checkWorkspacePosition(oldGeom);
+
+    // re-align geom_restore to contrained geometry
+    geom_restore = geometry();
+
+    // finally reset special states
+    // NOTICE that MaximizeRestore/QuickTileNone checks are required.
+    // eg. setting QuickTileNone would break maximization
+    if (maxMode != MaximizeRestore)
+        maximize(maxMode);
+    if (qtMode != QuickTileNone)
+        setQuickTileMode(qtMode);
+
+    ClientList tso = workspace()->ensureStackingOrder(transients());
+    for (ClientList::ConstIterator it = tso.constBegin(), end = tso.constEnd(); it != end; ++it)
+        (*it)->sendToScreen(newScreen);
+}
+
 } // namespace

layers.cpp

@@ -103,16 +103,8 @@ namespace KWin
 
 void Workspace::updateClientLayer(Client* c)
 {
-    if (c == NULL)
-        return;
-    if (c->layer() == c->belongsToLayer())
-        return;
-    StackingUpdatesBlocker blocker(this);
-    c->invalidateLayer(); // invalidate, will be updated when doing restacking
-    for (ClientList::ConstIterator it = c->transients().constBegin();
-            it != c->transients().constEnd();
-            ++it)
-        updateClientLayer(*it);
+    if (c)
+        c->updateLayer();
 }
 
 void Workspace::updateStackingOrder(bool propagate_new_clients)
@@ -851,6 +843,17 @@ Layer Client::belongsToLayer() const
     return NormalLayer;
 }
 
+void Client::updateLayer()
+{
+    if (layer() == belongsToLayer())
+        return;
+    StackingUpdatesBlocker blocker(workspace());
+    invalidateLayer(); // invalidate, will be updated when doing restacking
+    for (ClientList::ConstIterator it = transients().constBegin(),
+                                  end = transients().constEnd(); it != end; ++it)
+        (*it)->updateLayer();
+}
+
 bool rec_checkTransientOnTop(const ClientList &transients, const Client *topmost)
 {
     foreach (const Client *transient, transients) {

workspace.cpp

@@ -1217,41 +1217,7 @@ bool Workspace::isOnCurrentHead()
 
 void Workspace::sendClientToScreen(Client* c, int screen)
 {
-    screen = c->rules()->checkScreen(screen);
-    if (c->isActive()) {
-        screens()->setCurrent(screen);
-        // might impact the layer of a fullscreen window
-        foreach (Client *cc, clientList()) {
-            if (cc->isFullScreen() && cc->screen() == screen) {
-                updateClientLayer(cc);
-            }
-        }
-    }
-    if (c->screen() == screen)   // Don't use isOnScreen(), that's true even when only partially
-        return;
-    GeometryUpdatesBlocker blocker(c);
-    QRect old_sarea = clientArea(MaximizeArea, c);
-    QRect sarea = clientArea(MaximizeArea, screen, c->desktop());
-    QRect oldgeom = c->geometry();
-    QRect geom = c->geometry();
-    // move the window to have the same relative position to the center of the screen
-    // (i.e. one near the middle of the right edge will also end up near the middle of the right edge)
-    geom.moveCenter(
-        QPoint(( geom.center().x() - old_sarea.center().x()) * sarea.width() / old_sarea.width() + sarea.center().x(),
-            ( geom.center().y() - old_sarea.center().y()) * sarea.height() / old_sarea.height() + sarea.center().y()));
-    c->setGeometry( geom );
-    // If the window was inside the old screen area, explicitly make sure its inside also the new screen area.
-    // Calling checkWorkspacePosition() should ensure that, but when moving to a small screen the window could
-    // be big enough to overlap outside of the new screen area, making struts from other screens come into effect,
-    // which could alter the resulting geometry.
-    if( old_sarea.contains( oldgeom ))
-        c->keepInArea( sarea );
-    c->checkWorkspacePosition( oldgeom );
-    ClientList transients_stacking_order = ensureStackingOrder(c->transients());
-    for (ClientList::ConstIterator it = transients_stacking_order.constBegin();
-            it != transients_stacking_order.constEnd();
-            ++it)
-        sendClientToScreen(*it, screen);
+    c->sendToScreen(screen);
 }
 
 void Workspace::sendPingToWindow(xcb_window_t window, xcb_timestamp_t timestamp)